1. Field of the Invention
The present invention relates to an electro-penetrative type sludge weight reducing apparatus for dehydrating sludge. More particularly, the present invention relates to an electro-penetrative type sludge weight reducing apparatus including a sludge supplier, which can apply the same pressure stage by stage and apply the same voltage to uniformly dehydrate sludge, minutely and precisely control a compression height of sludge according to characteristics and a thickness of the sludge, and uniformly supply sludge having a desired thickness over an entire width of a conveyor belt to maximize an efficiency of reducing sludge moisture, and an insulation safety reinforcing electrode plate.
2. Description of the Prior Art
As generally known in the art, a polymer coagulant is added to sludge processed in wastewater and discharging water treatment plants in order to purify water and it is very difficult to dehydrate the sludge agglomerated by the polymer coagulant. Meanwhile, since disposal costs of sludge vary depending on a dehydration rate of the sludge, it is required to significantly reduce a content rate of the sludge in order to decrease costs or obtain a solid component of the sludge, which can be recycled as a fuel. The electro-penetrative type sludge weight reducing apparatus for reducing the content rate of the sludge according to the conventional arts as described above will be discussed in the following description. Korean Patent Application No. 1993-0010856 discloses an electro-penetrative type sludge weight reducing apparatus including a rotation drum having an anode electrode for removing water combined with sludge by an electric field, a compression belt having permeability of water configured to surround an outer circumference of the rotation drum, and a filter belt configured to be overlapped with surfaces of dehydration areas of the rotation drum and the compression belt. That is, the electro-penetrative type sludge weight reducing apparatus applies a constant voltage between the drum and the compression belt to form an electric field in the sludge, and thus separates water from the sludge and dehydrates the sludge. However, a method of applying a voltage to the rotation drum has a complicated structure and manufacturing process, and accordingly manufacturing costs are increased. Further, when high capacity sludge is processed, a large sized rotation drum is needed, which makes the maintenance of the apparatus and an accurate gradational control of an electrochemical reaction for dehydration difficult. Accordingly, Korean Patent Registration No. 10-0894266 for solving the aforementioned problem of the electro-penetrative type sludge weight reducing apparatus has been proposed. The proposed electro-penetrative type sludge weight reducing apparatus mainly includes a filter cloth 1600 for conveying sludge, and a sludge elevating means 1700 for pressurizing and dehydrating sludge supplied to the filter cloth 1600, a plurality of sludge elevating means 1700 being horizontally installed in a frame 1100. Meanwhile, the sludge elevating means 1700 having a plurality of rows are arranged in an upper portion of the frame 110 in a lengthwise direction. The sludge elevating means 1700 is operated to have the different numbers of sludge elevating means 1700 for pressurizing the sludge and different pressurization heights of the sludge elevating means 1700 by differently controlling pressures applied to the sludge according to characteristics of the sludge in a wastewater or a discharging water treatment plant. However, the characteristics of the sludge are changed according to seasons or environments, and widths of supplied sludge, so the pressure and the voltage applied to the sludge should be changed, but it is not easy to change the applied pressure and voltage in the proposed electro-penetrative type sludge weight reducing apparatus. Further, in a case of non-biodegradable sludge, an applied pressure should be minutely changed because of difficulties in dehydration, but the sludge elevating means 1700 arranged in a plurality of rows cannot minutely and precisely control the applied pressure and take up much space due to their long lengths in a lengthwise direction. Furthermore, since the sludge elevating means 1700 are arranged in a plurality of rows, the number of elevations for dehydrating the sludge is increased, and thus a dehydration processing time is increased, which creates problems in that dehydration throughputs are significantly reduced, manufacturing and installing costs of the sludge elevating means 1700 are greatly increased, and an operating method becomes difficult. Moreover, the sludge elevating means 1700 arranged in a plurality of rows cannot apply a constant and uniform pressure to an entire width of the sludge. That is, in pressurizing the sludge, a dehydration rate of the sludge is largely changed by a difference of a compression height of several mm, so that it is required to develop a technology, which can apply the same pressure to the entire surface of the sludge.
Further, it is preferable to minimize a water content rate indicating an amount of water contained in the sludge in order to process sludge from discharging water and wastewater or sludge from livestock excretions through methods such as burying, drying, or incineration in the ground, instead of disposing the sludge in the sea. For this purpose, apparatuses for removing moisture contained in the sludge by using various methods were developed in the conventional arts. For example, Korean Patent Application No. 10-2005-0108803 discloses a drum rotary typed electric dehydrator. That is, the conventional drum rotary type electric dehydrator applies direct current power to the sludge supplied to an inside of a drum to cause an electro-penetrative operation to the sludge, which reduces moisture of the sludge. Here, in order to reduce moisture of the sludge through the electro-penetrative operation as described above, it is preferable that sludge having a uniform thickness is inserted within the drum over an entire width of the electrode, but in the conventional arts, a separate equipment for implementing a uniform thickness of the sludge provided to the electric dehydrator did not exist, so that excessive abrasion of the electrode was caused in removing moisture and the excessive abrasion of the electrode caused a problem such as reduction of life spans of facilities.
Further, in a procedure of purifying water processed in wastewater and discharging water treatment plants, a polymer coagulant, which makes the sludge become an agglomerated state, is added, so that water purification is facilitated and a purification process becomes convenient. The agglomerated sludge should pass through a dehydration operation for removing moisture from the sludge for a processing since it contains much moisture. A work for reducing a water content rate of the agglomerated sludge through the dehydration operation corresponds to a very important process in an aspect of reduced disposal costs and possibility of various recycling. Further, when the water content rate of the sludge can be greatly reduced, the sludge can be recycled as a solidified fuel instead of being discarded. For this purpose, various methods are applied to the dehydration process of the agglomerated sludge. For example, the methods include a compressive type, which removes moisture by pressurizing the sludge, or an electro-penetrative type, which removes water through ion mobility. However, it is not easy to dehydrate the sludge by using the compressive type, which simply pressurizes the sludge, because the agglomerated sludge is a product generated by reacting with the polymer coagulant, and particularly, it is very difficult to significantly lower the water content rate of the sludge up to a degree where the sludge may be recycled as a solidified fuel, so the electro-penetrative type having a high dehydration capability is mainly used. The electro-penetrative type includes a rotation drum having an anode electrode and a compression belt having permeability of water configured to surround an outer circumference of the rotation drum. A voltage applied between the rotation drum and the compression belt forms an electric field and charged water moves to an opposite electrode of a sludge particle charge, so that the moisture is removed from the sludge. However, an electro-penetrative type apparatus having a rotation drum to which a voltage is applied requires a complicated structure, difficult manufacturing process, and high manufacturing costs, and also has difficulties in the maintenance as the apparatus becomes larger and difficulties in a gradational control of an electrochemical reaction when the apparatus is operated. Unlike the above, a horizontally conveying type electro-penetrative type apparatus can implement the same performance as the electro-penetrative type apparatus without the rotation drum by using a filter cloth for horizontally conveying sludge between electrode plates having +/− electrodes and applying compression and electric dehydration together. As described above, the horizontally conveying type electro-penetrative type apparatus has the same advantages of the rotation drum type apparatus without the rotation drum generating a magnetic field and simultaneously solves a disadvantage of the rotation drum type apparatus. Particularly, the horizontally conveying type electro-penetrative type apparatus provides an advantage of easy production and cheap maintenance costs for throughputs. The horizontally conveying typed electro-penetrative type apparatus requires that a first and a second electrode plate implement a stable electric field capability, a perfect insulation structure, and an easy assembly between many components, because the apparatus has characteristics of forming an electric field through the first electrode and the second electrode in an environment where the apparatus always contacts moisture while pressurizing horizontally conveyed sludge. However, the perfect insulation structure and the easy assembly structure are not compatible, so the first electrode and the second electrode applied to the horizontally conveying type electro-penetrative type apparatus has limitations in meeting both conditions while not increasing manufacturing costs. For example; when the perfect structure of the first electrode and the second electrode is focused upon, the number of components for a whole construction cannot help being increased and the assembly structure cannot help being complicated. On the other hand, when the easy assembly structure is focused upon, somewhat unsatisfactory insulation structure may be applied. When it is attempted to satisfy both conditions, price competitiveness is undermined.
Accordingly, it is required to develop and research an electro-penetrative type sludge weight reducing apparatus, which can solve the above mentioned problems.